The mitral valve is located at the junction between the left atrium and the left ventricle of the heart. During diastole, the valve opens, in order to allow the flow of blood from the left atrium to the left ventricle. During systole, when the left ventricle pumps blood into the body via the aorta, the valve closes to prevent the backflow of blood into the left atrium. The mitral valve is composed of two leaflets (the posterior leaflet and the anterior leaflet), which are located at the mitral annulus, the annulus being a ring that forms the junction between the left atrium and the left ventricle. The mitral valve leaflets are tethered to papillary muscles of the left ventricle via chordae tendineae. The chordae tendineae prevent the mitral valve leaflets from everting into the left atrium during systole.
Mitral valve regurgitation is a condition in which the mitral valve does not close completely, resulting in the backflow of blood from the left ventricle to the left atrium. In some cases, regurgitation is caused by dilation of the mitral annulus, and, in particular, by an increase in the anteroposterior diameter of the mitral annulus. Alternatively or additionally, mitral regurgitation is causes by dilation of the left ventricle that, for example, may result from an infarction. The dilation of the left ventricle results in the papillary muscles consistently tethering the mitral valve leaflets into an open configuration, via the chordae tendineae.